mm: only allow page table mappings for built-in zsmalloc

This allows to unexport map_vm_area and unmap_kernel_range, which are
rather deep internal and should not be available to modules, as they for
example allow fine grained control of mapping permissions, and also
allow splitting the setup of a vmalloc area and the actual mapping and
thus expose vmalloc internals.

zsmalloc is typically built-in and continues to work (just like the
percpu-vm code using a similar patter), while modular zsmalloc also
continues to work, but must use copies.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Gao Xiang <xiang@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Link: http://lkml.kernel.org/r/20200414131348.444715-12-hch@lst.deSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/Kconfig

@@ -707,7 +707,7 @@ config ZSMALLOC
 
 config ZSMALLOC_PGTABLE_MAPPING
 	bool "Use page table mapping to access object in zsmalloc"
-	depends on ZSMALLOC
+	depends on ZSMALLOC=y
 	help
 	  By default, zsmalloc uses a copy-based object mapping method to
 	  access allocations that span two pages. However, if a particular

mm/vmalloc.c

@@ -2047,7 +2047,6 @@ void unmap_kernel_range(unsigned long addr, unsigned long size)
 	vunmap_page_range(addr, end);
 	flush_tlb_kernel_range(addr, end);
 }
-EXPORT_SYMBOL_GPL(unmap_kernel_range);
 
 int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page **pages)
 {
@@ -2059,7 +2058,6 @@ int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page **pages)
 
 	return err > 0 ? 0 : err;
 }
-EXPORT_SYMBOL_GPL(map_vm_area);
 
 static inline void setup_vmalloc_vm_locked(struct vm_struct *vm,
 	struct vmap_area *va, unsigned long flags, const void *caller)